1. Field of the Invention
This invention relates to a low profile cable capable of the undercarpet transmission of electrical signals, fabricated of a flexible polymer for positioning around curves, and with an essentially flat central region and tapered wings extending outwardly therefrom.
2. Description of the Prior Art
Conventional multiconductor cables for transmitting high frequency electrical signals include both shielded twisted pair cables and coaxial cables. Such cables have their greatest utility in transmitting electrical signals between components. Such transmitted signals may be in digital form or in analog form.
Shielded twisted pair cables utilize a pair of insulated conductive wires in a twisted pair configuration with a grounded, electrically conductive shield around each twisted wire pair. The shield functions to reduce electromagnetic interference radiation, generally called EMI, which naturally emanates from signal transmitting wires and which might otherwise adversely affect the performance of adjacent electronic devices. Such shield also functions to minimize cross talk, electrical interference between one pair of wires and an adjacent pair which would tend to impair the fidelity of the signals being transmitted. Shielded twisted pair cables can constitute a type of a differential transmission system where both wires are electrically powered and both constitute signal carrying wires. The information transmitted is a function of the sequential voltage differential between the two wires of the pair. An example of a shielded twisted pair cable is described in U.S. Pat. No. 4,404,424 issued to King et al.
In a manner similar to shielded twisted pair cables, coaxial cables use an EMI shield to reduce radiation. But in coaxial cables, unlike shielded twisted pair cables, only one electrically powered signal wire is utilized. The signal wire is encased in insulation which is surrounded, in turn, by the grounded, electrically conductive shield. In coaxial cables, the shield also functions as a grounded reference for the voltage of the signal wire. An example of a coaxial cable is described in U.S. Pat. No. 3,775,552 issued to Schumacher.
Considerable effort has been expended to develop a flat coaxial cable which would yield the same performance characteristics as conventional coaxial cable but which would also enable the use of conventional mass stripping and termination techniques to thus facilitate the coupling of an electrical connector to the cable. Consider for example U.S. Pat. No. 4,488,125 to Gentry et al.
Other flat coaxial cables are disclosed in U.S. Pat. Nos. 4,487,992 and 3,775,552.
One application for flat cable is in under the carpet wiring situations in which a flat, low profile cable is extended beneath a carpet for connection to, and coupling of, components of an electrical system such as a computer system or the like. Shielded twisted pair cables do not have a low profile suited for use in undercarpet applications since twisted wires are continuously and sequentially located above, to one side, below, and to the other side of each other along the length of the cable. As a result, the cable thickness periodically increases to a double wire thickness along the length of the cable. This arrangement of signal wires thus precludes low profile cable configurations since low profile cable configurations are possible only in cables having their wires spaced parallel to each other in a single, usually horizontal, plane. The configuration and orientation of wires in a shielded twisted pair cable also precludes mass stripping and termination since the positioning of any one wire with respect to another varies as a function of where the cable is cut along its length.
While many types of cables have been proposed in the past, the invention disclosed herein contemplates a low profile, flat cable having the performance characteristics of shielded twisted pair cable but yet having a low profile suited for undercarpet installations. The flat cable disclosed herein also has the mass stripping and termination capabilities of other flat cable since its signal wires are consistently spaced with respect to each other and with respect to precise cable locations, unlike conventional shielded twisted pair cable. It is fabricated of a flexible elastomer with an essentially flat central region and tapered wings extending outwardly therefrom for positioning around curves.